1. Field of the Invention
This invention generally relates to the field of hand-held devices useful for respacing the racket strings of tennis, racquetball, squash or badminton rackets. The present invention is particularly directed towards a portable hand-held tool to be used off and on courts, during breaks in play, to realign the vertical and horizontal positions of racket strings which have moved during the game.
2. Brief Description of the Prior Art
A tennis racket principally consists of a head, a throat and a handle. The head includes a set of horizontal and vertical strings and a frame, wherein the frame is used for supporting the set of strings. The strings are interlaced in a spaced-apart 90-degrees crossing pattern. The shape of the frame and the vertical and horizontal spacing of the tennis strings determines the position of the "sweet spot", a hitting area in the center of the racket head, of that particular design of the racket.
When the racket is initially strung, the tension of the strings is carefully controlled in accordance with the skill and preference of a player. Normally, the vertical and horizontal strings are stretched to a tension of between 55 and 70 pounds, but some players prefer a lighter tension, as low as 40 pounds. No matter how low or how high the tension is set in the stringing process, during play the crossing pattern of the strings gets frequently disturbed. When this happens, one or more strings near the center of the head area are moved away from their usual 90-degrees crossing pattern.
When a string is stretched to a moved position, away from its original position, it becomes elongated. With the change in strings elongation, the original tension of the strings in the racket is modified. This modifies the hitting properties of the racket and consciously or unconsciously affects the player's control of the ball. As the ball leaves the surface of the racket, the direction and velocity of the traveling ball in its path of travel is changed.
During each play, the impact of the ball upon the strings when a shot is made often distorts the strings from their original spacing. The degree of distortion is a result of the speed of the ball, when making contact with the racket string, and the angle of the racket at which the player strikes the ball. The distortion repositions the area of the "sweet spot" and makes the player loose confidence in his shot. In addition, strings can come out of alignment with each other after only a few strokes of the tennis racket in play, due to modern high velocity hits and techniques where the tennis ball is not struck flush but instead is struck at an angle in order to import substantial ball spin or for angular direction.
It has been recognized that it is desirable to keep the strings of a racket in proper alignment with each other during play in order to provide optimal racket efficiency and string durability. Therefore, it is desirable to control the position of the individual strings in the crossing string pattern as closely as possible and to keep their original positions at all times, in order to maintain the designed tension in the hitting area in the head of the racket.
There is a need for a simple, portable tool enabling players to return the horizontal and vertical racket strings to the original "sweet spot", in order to ensure consistency of ball direction and force and accuracy of shots. Further, this will reduce tendency of the strings to take a permanent set and lose their tension due to stretching, if they are left in a distorted position for long periods of time, and to reduce the time between restringing the racket, due to the stretching of the strings and softening of their original tension, from the time when they were first installed or restrung.
Large, complex, bulky and expensive string straighteners have been available for a while, and are kept on the court sidelines. However, although helpful, these advances in the design are inflexible and unable to cover players' needs occurring during game. In most instances, when strings become misaligned, the player must resort to finger tuning the racket, by manually moving the strings to their approximately proper positions from time to time, when he or she has completed their active playing session.
Lately however, portable realigning tools are becoming popular, due to ever increasing demand for repositioning of racket strings during game. These portable devices presently utilized range from simple to very complex. For example, U.S. Pat. No. 4,752,071 issued in 1988 to Tobach discloses a simple portable hook which is used to straighten only one string opening at a time. Its use takes considerable time if, as is usually the case, a number of strings are out of alignment.
U.S. Pat. No. 4,489,942, Kent, granted in 1984, discloses a device for aligning strings in the grid of a tennis racquet. The device is comprised of a base which has a peripheral groove for receiving the frame of the racquet. The base has a plurality of posts arranged and shaped to intersect the spaces between strings. A tooth is hinged to the base and acts as a press to force the tennis racquet down on the posts, causing mislocated strings to become aligned.
Redrow U.S. Pat. No. 5,035,429 from 1991 for String Straightener For Tennis Racket describes a straightener that automatically adjusts itself to the model of the racket. The device has a plurality of flexible, narrow, tight-knitted teeth with V-shaped edge. The teeth are flexible and two or more teeth can fit in the same space between the strings.
Short U.S. Pat. No. 5,207,423 from 1993 for Tennis Racket String Straightener relates to a tool with triangular, wide teeth that are either placed apart by the same distance or with gradually increasing distance.
Herbert U.S. Pat. No. 4,733,866 from 1988 depicts a Portable String Aligner For Rackets. Their tool has replaceable, variously sized pegs with pyramidal, bullet, or bevelled ends.
Chan U.S. Pat. No. 5,310,181 from 1994 describes a Racquet String Aligner. This invention is described as placed on a ball container cap. The pegs are pyramidal and placed in two-dimensional rows and columns.
Ho U.S. Pat. No. 4,776,591, describes a comb-like aligner with unconnected teeth and with a string receiving notch. The teeth are pyramidal.
Macknigg U.S. Pat. No. 5,310,182 from 1994 describes a string adjuster with one or more rollers rotatingly moving the strings in a very fast fashion.
The U.S. Pat. No. 4,089,523 to Newburger et al. shows a plate having fixed teeth of a pyramidal shape, adapted to move strings back into their original positions when pressed into the openings in the crossing pattern.
Some simple devices, mentioned above, may be adequate, assuming that the spaces between the strings and their shapes are all of a standard pattern. However, many of the tennis rackets in use today are strung with different crossing string patterns, using differently spaced strings, and there seems to be no standard for shapes or sizes of spacings between the horizontal and vertical strings in many of the modern rackets.
Therefore, several patents mentioned earlier, like the U.S. Pat. Nos. 4,733,866 to Herbert and 4,776,591 to Ho, show string straightening means for use on different tennis rackets, that may have strings spaced apart in different patterns. In each of these respective patents, adjustably mounted string engaging pegs or teeth are described, which must be adjusted to fit the particular string arrangement of each racket upon which the respective device is to be used. After the location of pegs or teeth has been chosen and they have been individually moved to a proper setting, they are locked in place for cooperating with the strings.
The existing racket string straightener devices require a great deal of time and patience to return the strings to their proper place, because these devices must be readjusted several times to cover the strings across the entire face of the racket.